Cardiac surgery was initially undertaken using highly invasive open procedures. A sternotomy, which is a type of incision in the center of the chest that separates the sternum, was typically employed to allow access to the heart. In the past several decades, more and more cardiac operations are performed using intravascular or percutaneous techniques, where access to inner organs or other tissue is gained via a catheter.
Intravascular or percutaneous surgeries benefit patients by reducing surgery risk, complications, and recovery time. However, the use of intravascular or percutaneous technologies also raises some particular challenges. Medical devices used in intravascular or percutaneous surgery need to be deployed via catheter systems, which significantly increase the complexity of the device structure. As well, doctors do not have direct visual contact with the medical devices once the devices are positioned within the body.
One example of where intravascular or percutaneous medical techniques have been employed is in the treatment of a heart disorder called atrial fibrillation. Atrial fibrillation is a disorder in which spurious electrical signals cause an irregular heartbeat. Atrial fibrillation has been treated with open heart methods using a technique known as the “Cox-Maze procedure”. During various procedures, health care providers create specific patterns of lesions in the left or right atria to block various paths taken by the spurious electrical signals. Such lesions were originally created using incisions, but are now typically created by ablating the tissue with various techniques including radio-frequency (RF) energy, microwave energy, laser energy, and cryogenic techniques. The procedure is performed with a high success rate under the direct vision that is provided in open procedures but is relatively complex to perform intravascularly or percutaneously because of the difficulty in creating the lesions in the correct locations.
Preparation of catheter device systems for subsequent delivery through a bodily opening leading to a bodily cavity (e.g., as required by some percutaneous or intravascular procedures) may require that various undesired fluids (e.g., air) be purged or otherwise removed from portions of the systems prior to insertion into the body. Failure to do so may allow for a transfer of at least some of the undesired fluids to within the body, which may, in turn, result in various undesired outcomes (e.g., the formation of various air embolisms). Various catheter device systems employ various features that can act as fluid traps from which undesired fluid can be difficult to remove therefrom. For example, various lumens comprised by various catheter device systems may act as fluid traps.
In this regard, FIG. 7A is a schematic representation that shows at least part of a conventional catheter system that includes a catheter sheath 812 including a lumen that provides a passageway for a catheter (e.g., dilator catheter 800) delivered through a bodily opening during a medical procedure. In this regard, the catheter sheath (e.g., 812) is a member that is inserted into the body to shield the body from potential damage that may be caused by the delivery of a catheter introduced into the lumen of the catheter sheath. The catheter can take various forms. For example, the catheter can be an introducer or dilator (e.g., dilator catheter 800). The catheter (e.g., dilator catheter 800) is typically inserted through the lumen of the catheter sheath 812 from the proximal end 812a of the catheter sheath 812 to the distal end 812b of the catheter sheath 812. A tapered or point-like end 813 of the dilator catheter 800 typically protrudes from the distal end 812b of the catheter sheath 812 in a state in which the dilator catheter 800 is operably inserted into the lumen of the catheter sheath 812. The dilator catheter 800 and catheter sheath 812 assembly may then be advanced through the bodily opening with the tapered or protruding point-like end 813 of the dilator catheter 800 dilating or enlarging various parts of the bodily opening to facilitate the advancement of the assembly through the bodily opening. In some cases, the dilator catheter 800 and catheter sheath 812 assembly is advanced over a previously deployed guidewire to help guide the assembly to a desired location within the body of the patient. Once the assembly has been successfully delivered through the bodily opening to the desired location within the body, the dilator catheter 800 (and the guide wire if employed) is pulled out of the catheter sheath 812 leaving the catheter sheath 812 behind in the bodily opening. Each of one or more additional catheters (e.g., treatment or diagnostic catheters) or other medical instruments may then be advanced through the lumen of the catheter sheath 812 to the desired location within the body.
As discussed above, undesired fluid (e.g., air) may be trapped or otherwise present, for example, in the lumen of the catheter sheath 812, at least before or after the insertion of the catheter (e.g., dilator catheter 800) into the lumen. This undesired fluid requires removal (e.g., to avoid introducing the undesired fluid into the body) prior to advancement of the assembly of the dilator 800 and catheter sheath 812 through the bodily opening. Conventional catheter systems attempt to flush the undesired fluid by introducing a benign fluid, such as saline, into the region of the lumen of the catheter sheath 812 to flush the lumen of the undesired fluid. The introduction of fluid (e.g., saline) into the lumen of the catheter sheath 812 to remove the undesired fluid therefrom may occur at least before the insertion of the catheter (e.g., dilator catheter 800) into the lumen or after the insertion of the catheter (e.g., dilator catheter 800) into the lumen.
FIG. 7B shows a typical flushing procedure employed by conventional catheter systems. A source 802 of benign flushing fluid 804 (e.g., saline) is fluidically connected to the catheter sheath 812 at a location at least proximate the proximal end 812a (e.g., at supply connector 812c) to attempt to flush a region of the lumen between the dilator catheter 800 and the catheter sheath 812. It is noted that conventional flushing systems flush proximally (near proximal end 812a) toward distally (toward distal end 812b), because the supply connector 812c for the benign flushing fluid is provided proximally and not distally on the catheter member. In conventional flushing systems, a distal supply connector (e.g., a distal connector located proximate the distal end 812b of catheter sheath 812 rather than proximate proximal end 812a) would interfere with the introduction of the catheter member into the bodily opening and is therefore not employed. It is noted that even if the lumen of the catheter sheath 812 is filled with the benign flushing fluid, the introduction of the dilator or other catheter into the lumen may introduce undesired fluid into the lumen of the catheter sheath 812, thereby further complicating the flushing procedure.
As minimally invasive medical procedures are becoming more prevalent and use more complex catheter-based devices is increasing, a greater awareness for safety is materializing, leading to a greater sensitivity to air bubble ingress into the body (e.g., vascular system). The known art consists of passive and active radial seals that attempt to seal the lumen of the catheter sheath 812 against the outer circumference of the dilator catheter 800 (e.g., during vascular access and catheter sheath placement), and to seal against the outer circumference of a treatment or diagnostic catheter interchanged with the dilator catheter 800 during advancement, during retraction, and during any diagnosis or therapy delivery associated with the treatment or diagnostic catheter.
For example, in FIG. 7A, radial seal 815 is employed to seal around a circumferential surface of dilator catheter 800. These radial seals are also required to seal the lumen shut during an exchange between the dilator catheter and another catheter, (e.g., after the catheter sheath is positioned in the body and before a second catheter is advanced through the catheter sheath). It is important to note that these radial seals may need to seal against both pressure gradients arising outwardly from the body as well as inwardly into the body. For example, in cardiac applications, the radial seals may need to seal against both pressure gradients arising outwardly from the vascular system outwards, as well as inwards into the vascular system, depending on the location of the distal end 812b of the catheter sheath 812 in the body, the time point in the cardiac cycle, the blood pressure, and the elevation of the proximal end 812a of the catheter sheath 812 above the distal end 812b. 
These radial seals are typically required to be made of deflectable and deformable materials that can create a seal around a large variance in diameter and are therefore limited by how large they can grow. Having two radial seals in series, one optimized to seal around a small diameter and another optimized to seal around a larger diameter, is also known in the art, but this solution suffers from the problem of having air bubbles caught in between the two radial seals and not having sufficient control of the air to be certain that it does not advance into the body. Due to limitations of materials, the seals known in the art have limitations with respect to the largest diameters they can function on effectively, attempting to balance friction on the dilator catheter or additional catheter with sealing pressure in a state in which the lumen is empty of any catheter, balancing usability against patient safety.
There is, therefore, a need in the art for improved solutions for eliminating undesired fluid, such as air, from various catheters and from within the lumens of catheter sheaths.